Jack lives in his parents' basement, which he uses as his secret lab. His parents are never seen, nor were they mentioned that much in the series. However, it has been shown that his parents (or his father at least) appear to be involved in some high position or profession, as they appear to be relatively wealthy. He also has a blond cousin Megan, who is much younger than he and is aligned with the Xiaolin.
Starting with the second season, Jack becomes more of a scared, whiny, fanboy than he was in the first season where he acts more as a psychotic villain beginner and was much calmer.
Examples of Jack's "evil heroes" are Chase Young and Hannibal Roy Bean. He looks up to those evil heroes and tries to form partnerships with them, usually ending up with him getting hurt.
At times, he has gone into the Ying-Yang World, losing his evil side and coming out as a "good Jack," who is quirky, spunky, dramatic, and what can only be described as the ultimate good. After this happened in "Saving Omi," Good Jack went back into the Ying-Yang World. He then used the Ring of the Nine Dragons to duplicate himself, and only one of these clones left. Because this clone only used the Yang Yo-Yo to leave, he regained his evil chi, essentially going back to normal Jack. Good Jack appeared again in the episode "The Life and Times of Hannibal Roy Bean" when regular Jack found the prison that held Hannibal Roy Bean. Hannibal tricked not Jack, but the monks, into letting him out by using the Moby Morpher to turn into Jack. Hannibal (still in disguise) wasn't found out until the monks ran into regular Jack as well as Good Jack. In order to identify the fake, they used the Ring of the Nine Dragons to reunite the two correct Jacks.
Later in the episode "Hannibal's Revenge" Kimiko disguises herself into looking like Jack in order to win a showdown. In the last episode Jack is left with his favorite Shen Gong Wu, the Monkey Staff.
Skills and abilities
Super-Genius Intellect: As unbelievable as it sounded, in his own idiotic way, Jack's most dangerous weapon was his genius-level intellect. He was easily one of the top mortal minds on the planet as he was able to create hundreds of devices, including a working time machine and a Shen Gong Wu detector. His most frequently used robots were the Jack-Bots, floating robots, equipped with saws, machine guns and any other kinds of weapons.
- Scientific and Robotic Mastery: Jack was a robotic-engineering and scientific genius, and commands an army of Jack-Bots. He occasionally modified them to have better defenses, new weaponry, or alterations appropriate for the setting. He invented a time machine, although it required the Eye of Dashi for power. He developed a Shen-Gong-Wu-locating sensor, allowing him to find Shen Gong Wu without Wuya's help.
Figure Ice Skating: He had ice skating lessons that came in handy in an off-screen showdown.
Fly: Because of his helibot from his grandmother, he can use it to fly around.
Well Connected: As shown in the last episode, he (supposedly) was able to gather nearly every single villain that the monks have ever faced, including Chase Young, who considered Jack incompetent, Hannibal Roy Bean, also considered Jack incompetent, and Wuya as well. This showed that he at least had good enough connections to them to cause every single one of them to launch a full attack on the monks.
High Physical Abilities: While not a warrior, he had shown above-average physical attributes in his showdowns and Shen Gong Wu hunts. Without his robotic minions, he was largely defenseless against the appreciably stronger Xiaolin Warriors. Despite almost constant defeats at the hands of his enemies and rivals from both sides, he remained persistent, coming to nearly every Shen Gong Wu location.
Jack has had many, many allies. In chronological order, they are listed here:
- Xiaolin Monks (to stop Wuya)
- Jack Spicer's Evil Dreamteam
- Chase Young
- Hannibal Roy Bean
- Although Wuya had conquered the world two times and was the most powerful being in the universe in her human form, Jack seemed to respect Chase and Hannibal more than her and he even affiliated with the Xiaolin Monks to defeat her.
- As seen in the Xiaolin Chronicles episode "Laws of Nature", Jack is allergic to liver.
- With the exception of The Return of Master Monk Guan, Jack has appeared in every episode of every season.
- He expressed a romantic interest in Kimiko in the episode Chameleon, but this is never mentioned again after that episode.
- He also seemed to be the one who assembled all the villains at the end of Time After: Time Part I, meaning that the monks' oldest enemy may also be their most dangerous.